1. Field of the Invention
The present invention generally relates to a QoS (Quality of Service) information notification method, a communication apparatus and an inter-domain signaling apparatus for transmitting QoS information over a multi-domain network.
2. Description of the Related Art
As the Internet has been playing an important role as a communication infrastructure, there are growing demands for QoS such as a bandwidth or a delay time for applications. For example, there are a growing number of broadband applications or services such as a video delivery application/service and a video conference application/service. However, because technologies for guaranteeing end-to-end QoS such as a bandwidth or a delay time have not been introduced into the Internet, telecommunication carriers and network providers try to avoid degradation of services by increasing data rate. Because it is necessary to increase bandwidths in order to increase data rate, it is desirable to guarantee QoS by allocating appropriate communication resources in response to the user's request. In addition, there are growing expectations for high quality VoIP (Voice over Internet Protocol) services over telecommunication carriers' networks. Thus, there are growing demands for providing a QoS service over the telecommunication carriers' networks, which is equivalent to the conventional circuit-switched telephone service rather than the conventional IP phone.
Further, when such high quality services are provided by the telecommunication carriers, there are also growing demands for the high quality services to be provided among different telecommunication carriers (i.e. domains). Communications among multiple domains occur when communication begins between physically separated terminals and passes through multiple telecommunication carriers. For example, such communication occurs when a user places an international TV phone call or when a user receives a video delivery service from a telecommunication carrier other than the user's subscribing telecommunication carrier. A network including multiple domains is referred to as a multi-domain network.
For a single-domain network, there have been developed many technologies for guaranteeing QoS for each of network technologies. For example, in the case of ATM (Asynchronous Transfer Mode), QoS is guaranteed by means of a virtual connection and a virtual path. In the case of IP (Internet Protocol), specifically Intserv defined by IETF (Internet Engineering Task Force), the bandwidth over IP networks is reserved by means of RSVP Protocol (Resource Reservation Protocol) for each session. In the case of Diffserv defined by IETF, although it is not possible to guarantee QoS for each session, it is possible to provide differentiated services by differentiating QoS for each group of flows.
On the other hand, for the multi-domain network, desired QoS is not always guaranteed, because of either different communication technologies for each domain or different mechanisms for providing the QoS service for each user. Therefore, on the user's request for QoS, network elements have to determine whether QoS can be guaranteed or not, and be configured depending on either communication technologies for each domain or mechanisms for providing the QoS service.
There are some technologies for guaranteeing QoS over such multi-domain network. Conventionally, when the network accepts a QoS request from the user, the QoS request is accepted sequentially for each domain, and then a resource is allocated to the QoS request. For example, Japanese Laid-Open Patent Application No. 2001-282760 (Reference 1) discloses a multi-domain service broker which configures QoS for each domain. Further, Japanese Laid-Open Patent Application No. 2002-344499 discloses an intermediate bandwidth allocation server which reserves a bandwidth along multiple service providers.
FIG. 1 shows a method of guaranteeing QoS in accordance with Reference 1. When a management apparatus (A) accept a QoS request from a user (S1), the management apparatus (A) requests the multi-domain service broker to send the instruction to management apparatuses in the other domains (S2). When the management apparatus (A) receives the response to the instruction (S3), it negotiates with the next management apparatus (B and/or C) in the other domain (S4). Then, each management apparatus makes a configuration for QoS (S5), the management apparatus (A) sends the response (S6), and communication is established (S7).
Thus, when constructing a QoS route over the multi-domain network, the management apparatus has to know which domains support a QoS service in advance. Typically, whether the domain supports the QoS service or not depends on the service policy for each domain. For this reason, it is expected that some of multiple domains do not provide the QoS service due to their service polices. In order to know which domains support the QoS service in advance, telecommunication carriers may exchange information on the availability or the content of the QoS service with each other. However, when one of the domains starts to support the QoS service, or when the content of the QoS service changes, for example, it is necessary to check activities among telecommunication carriers in order to exchange information, which results in taking time and costs for the checking activities.